Washington County leans heavily Democratic by roughly 32 points: about 66% of voters vote Democratic and 34% Republican.
About 72% of adults in Washington County typically vote, above the U.S. average of about 62%. Among adults in Washington County, ~48% vote Democratic, ~24% Republican, and ~28% don't vote. The map below shows estimated turnout by block group.
How Washington County compares
Among counties within 50 miles, Washington County leans more Democratic than 9 of 10 neighbors.
Washington County runs about 18 points more Democratic than Oregon as a whole.
Politics vary noticeably by city within Washington County. The east side runs the most Democratic (D+47) and the southwest side runs the most Republican (R+11), a spread of about 59 points.
Why Washington County leans the way it does
This analysis examined 14,881 data points per county to find what predicts political lean and turnout. The items below are a few correlations that stood out for Washington County, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 87% of residents in Washington County live in densely developed areas, about 51 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Washington County sits in the top quarter (about 48%, above 96% of counties).
Paved land cover and Democratic lean
Places with extensive paved surfaces tend to lean Democratic; Washington County, OR sits in the top tenth nationally on this measure. Paved ground does not change how people vote; it mostly reflects how urban and built-up a place is.
Why turnout in Washington County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Washington County is in the top quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. The dental-visit rate here is about 67%, about 7 points above the U.S. average of 60%. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Multnomah County, OR D+52
- Clackamas County, OR D+13
- Clark County, WA D+7
- Yamhill County, OR R+5
- Columbia County, OR R+18
- Marion County, OR D+3
- Polk County, OR R+4
- Cowlitz County, WA R+18
- Skamania County, WA R+13
- Tillamook County, OR R+9
Counties with Similar Populations
- Brevard County, FL R+19
- Williamson County, TX Even
- Johnson County, KS D+9
- Anne Arundel County, MD D+17
- Baltimore City, MD D+72
- Douglas County, NE D+17
- Jefferson County, CO D+18
- Montgomery County, TX R+35
- Bristol County, MA Even
- Delaware County, PA D+27
Sources and methodology
Precinct-level voting records used to fit the model come from Oregon Secretary of State, Elections Division, distributed by the Voting and Election Science Team. Demographic inputs come from the U.S. Census Bureau (ACS 5-year estimates and the 2020 Decennial Census). Health and environmental inputs come from the CDC (PLACES and the Environmental Justice Index). Land cover comes from the USGS and EPA. Election-day and lead-up weather come from PRISM 4km daily grids and the NOAA Global Historical Climatology Network. Mail-voting and election-administration patterns come from the MIT Election Lab's Survey of the Performance of American Elections. Block-group crime detail comes from CrimeGrade. Internet data and modeling support provided by ISPreports.org.
Modeling and analysis by the BestNeighborhood data science team. Full methodology and findings: political spectrum map.
Methodology reviewed by the BestNeighborhood data team. Last updated May 2026.